Method for texturing non-porous woods to resemble porous woods



Nov. 2, 1965 A. ELMENDORF 3,214,870

METHOD FOR TEXTURING NON-POROUS WOODS TO RESEMBLE POROUS WOODS Filed July 27, 1962 2 Sheets-Sheet 1 INVENTOR.

Nov. 2, 1965 A. ELMENDORF 3,214,870 D OR TEXTURING NON-POROUS WOODS TO 2 Sheets-Sheet 2 Filed July 27, 1962 I NVENTOR. flw/m ar/f United States Patent M Illinois Filed July 27, 1962, Ser. No. 212,900 7 Claims. (Cl. 51281) This invention relates to a method for treating the surface of a non-porous wood panel to cause it to resemble the surface of porous wood.

A primary purpose of the invention is a method of cansing the surface of a non-porous wood of the coniferous type, having conspicuous annual rings, to resemble the surface of a ring-porous wood, with particular reference to the conversion of the surface of Douglas fir plywood to resemble the surface of ring-porous wood.

Another purpose of the invention is to convert a wood surface having no pores, or inconspicuous pores, into a surface provided with numerous short grooves, randomly distributed, resembling open pores in the surface of a porous wood.

Another purpose of the invention is to convert the surface of Wood of the gyrnnosperm family to resemble the surface of wood of the angiosperm family.

Another purpose of the invention is to provide a panel composed of ligno-cellulosic fibers with conspicuous, discontinuous, and irregularly spaced grooves that remain visible when the panel is given a printed wood grain finish resembling that of a porous wood.

Other purposes will appear in the ensuing specification, drawings and claims.

The invention is illustrated diagrammatically in the following drawings wherein:

FIGURE 1 is a diagrammatic illustration of one method for gouging the surface of a wood panel to form short grooves of irregular lengths and widths, randomly distributed.

FIGURE 2 show a second method for producing short grooves on the surface of a panel, the grooves again being of irregular length and width and randomly distributed,

FIGURE 3 shows a third -method for obtaining short grooves of the type described,

FIGURE 4 shows a plan view of a portion of a Douglas fir plywood panel which has been gouged by any of the methods shown in FIGURES l, 2 and 3, and

FIGURE 5 shows a plan view of a Wood surface after grooving by any of the methods illustrated in FIGURES l, 2 and 3.

In FIGURE 1, a wood fiber panel 1, which may be Douglas fir plywood or any other non'porons wood, may be moved by a rotating cylinder 2, or by means of a con veyor belt as in conventional sanding machinery. A small cylinder 3 may be surfaced with a coarse grit embedded in a paper or cloth 4 wrapped around the cylinder. A yielding cushion 5 may be positioned between the cylinder and the wrapping 3.

The radius of the cylinder 3 should be substantially smaller than that of conventional sanding drums and the tangential speed of the surface carrying the grit should be below the speed of the grit in a conventional sanding machine. The speed of movement of the panel 1 may be the same as that of panels moving through a conventional sanding machine. The grit is substantially coarser than the grid generally used in sanding plywood panels. As an example, satisfactory results were obtained when the radius of the drum or cylinder 3 was 1 /2 inches, and the speed of the grit 600 feet per minute, with a speed of movement of the panel of 60 feet per minute, in other words, with a ratio of grit to panel speed of about 1. If a belt is used to increase the distance a grit particle travels 3,214,870 Patented Nov. 2, 1965 before it again contacts the panel surface, the ratio of grit speed to board speed may be greatly increased. Good results are then obtainable With a ratio of 100:1.

In FIGURE 2, the grit may .be carried by a moving belt 6 actuated by mechanical means as in conventional wide belt sanding machines. The panel 7 may be moved by mechanical means as in conventional sanding machines. Numerous coarse granules of the type used on coarse sand paper are bonded to the surface of the belt 6 which moves through an are about pressure roll 8. The radius of the roll 8 should be comparable to the radius of drum 3. Good gouging or grooving of the panel surface is obtained with conventional aluminum oxide or silicon carbide grit of size =16 to 60, the granules being preferably distributed on the surface of the belt as in open-coat sandpaper. The pressure roll 8 bearing on the belt is preferably provided with a thin cushion surface 9 to accommodate minor unevenness in thickness of the panel 7 and may rotate with the same surface speed as that of the moving belt.

FIGURE 3 shows another method of gouging the surface of a wood or plywood panel to obtain short grooves being of irregular lengths and widths and being randomly distributed. A belt 10 may be actuated as in wide belt sanding machines. It is provided with coarse grit as in FIGURE 2 but instead of bending to an are produced by a rotating cylinder the belt carrying the grit is bent at the point of contact, a radius comparable to the radius used in FIGURES l and 2, by means of a shoe 11. A cushion 12 may be surfaced with a graphite impregnated cloth l3 of the type commercially used to reduce belt friction in conventional wide belt sanding machines. The cushion 12 accommodates minor variations in thickness of a panel 14- driven by a conventional roller 15.

In commercial operation of drum sanding machines, plywood panels which are being sanded generally move at a speed of 20 to 30 feet per minute. In wide belt sanding machines, the panel may move from 20 to feet or more per minute. The surface speed of the sanding medium is generally at least 4000 feet per minute. Experience has shown that if coarse grit is used for sanding purposes in either type of sanding machines, the effect is to groove the surface of the panel with continuous long grooves. Such grooves are acceptable for some decorative panels but are highly objectionable in sanding plywood panels as a smooth surface is always desired for commercial plywood panels. The continuous grooves result from the fact that at the point of contact With the panel a particle or grit in both the drum sanding machine and the wide belt sanders will move in a straight line substantially parallel to the surface of the panel, thereby scratching or gouging the surface with a groove of considerable length. Due to the high speed of the sanding medium a particule or grit on its next passage over the panel surface Will connect up with the groove previously formed thereby providing a continuous channel when this is repeated over and over again. The result is a striated surface, and not a surface of scattered, short, discontinuous and unconnected gashes.

The straight line grooves resulting from coarse sandpaper used on conventional wide belt sanding machines results from the fact that at the point of contact with the panel, the belt moves under a flat pad, and in the case of the sanding drum the large diameter of the drum combined with the cushioning provided between the drum and the sandpaper, produces the effect of a fiat pad.

I have found that if instead of moving in a direction parallel to the surface of the panel for an appreciable dis tance, the grit is caused to move through an arc, the surface is then gouged with short grooves, tapering at the two ends in the form of a shallow crescent.

This crescent can be lengthened if the panel moves dur ing the time of contact with a given grit particle. It

in shade and harder.

is important to note that the grooves formed by the granule on its next passage must not connect with the previous groove. In other words, a time interval must be provided during which the panel moves while the granule in question is out of the groove and is on its path of return to the panel. This time interval must be adequate to prevent the optical impression of groove alignment. The larger the end-to-end distance between grooves, the more satisfactory the optical separation. I have found, for example, that when a belt feet long moves at a speed of 650 feet per minute, and the panel moves at 60 feet per minute in the same direction, and if the belt passes over an arc of 1 /2 inches radius at the point of contact, there is no apparent connection between the grooves produced by a given grit in successive passes over the panel surface. Further improvement in this respect is provided if the belt is moved laterally at frequent intervals so that the path of a given granule is shifted sidewise during its passage from one groove to the next.

The gashes or grooves may be as short as /8 inch or as long as two to three inches depending upon the ratio of speed of grit to speed of panel, and distance travelled by the grit from one contact with the panel to the next. Observation of typical hardwoods with conspicuous pores shows that the length of the pores exposed on the surface may range from inch to about three inches.

The panel may move in the direction of the movement of the grit or in the opposite direction. The only effect is to alter the ratio of the speed of the grit to the speed of the panel. Suffice to say that the ratio of the speed of the grit to the speed of the panel must be less than the ratio used in conventional d-rum and wide belt sanding machines. This speed reduction, combined with the fact that each granule moves through an arc of small radius at the point of contact, produces the results desired.

As the coarse grit used is of non-uniform size and is randomly distributed over the moving surface to which it is bonded, the resultant narrow gashes are also randomly distributed and of various widths and lengths. Note the grooves 16- in FIGURE 5.

It will be noted in analyzing the anatomy of rotarycut veneer obtained from soft woods such as Douglas fir, that at the junction of the spring wood with the summer wood the thickness of the spring wood tapers off to a feathered edge. Note FIGURE 4 in which the spring wood is indicated at 18. Coarse grit of the type described, moving over an are at the point of contact with the wood surface will cut through the feathered edge of the spring wood 18, producing a jagged line at the junction with the summer wood 17. The spring wood removed by many of the granules or grits reveals the presence of the underlying summer wood which is darker Smaller particles that will produce small grooves in the spring wood may produce no appreciable scratching of the summer wood. Large particles cut deep grooves in the summer wood that may extend into the spring wood.

The summer wood area 17 illustrated in FIGURE 4 may be darkened and made more conspicuous by the .chemical treatment described in my co-pending applica tion Serial No. 185,018. When the summer wood has been darkened by this treatment, only the surface is darkened. The bottom of the grooves, whether we reveal summer wood or spring wood, are lighter in shade than the flat surface areas of the summer wood contacted by the hot rolls used in treating the wood. The chemical treatment does not introduce a conspicuous change in the color of the spring wood, whereas it does change the color of the summer wood, except within the grooves.

It should also be noted that where the spring wood feathers out over the summer wood, the grooves may be out through the spring wood thereby revealing the underlying summer wood. Where the summer wood feathers out and overlaps the spring wood the grooves cut through the summer wood may reveal the underlying spring wood. Since the spring wood and summer wood are always different in shade, the junction of the two will appear jagged.

Various optical effects are obtainable by filling the grooves with a white or light colored filler. The coarser grooves at the junction of the spring wood with the summer wood may be filled with the filler, thereby accentuating the jagged line. By using a light colored filler resembling in shade the shade of the spring wood, the filled grooves in the surface of the spring wood will become inconspicuous and the general appearance of the spring wood is substantially the same as if it had not been grooved. In contrast, the grooves cut into the surface of the summer wood will become conspicuous, giving the impression of a ring porous wood.

The wood surface may also be stained to resemble the color of another wood such as oak, and a dark filler may be used. A dark brown stain applied to the surface of a grooved Douglas fir plywood panel may be absorbed to such an extent by the spring wood that it assumes a darker shade than the summer wood. The short gashes in the summer wood may cut through the summer wood revealing the spring wood, and when stained, they are darker than the summer wood and resemble the medullary rays that are so characteristic of oak. The darkened spring wood and the jagged junction line with the summer w-ood suggest the appearance of a ring of pores as in oak. Many combinations of shade can be obtained due to the fact that the spring wood is more readily stained and is more absorptive of the stain than summer wood.

The grooving or gouging process shown may also be used on other ligno-cellulosic boards, for example hardboard or the like. The grooved surface may then have a wood grain pattern printed thereon. Preferably the wood grain pattern should be printed in such a way that the grooves are not noticeably filled.

In summary, the short grooves produced by the various methods illustrated in FIGURES 1, 2 and 3 when applied to a non-porous wood particularly when filled with a colored filler or stain result in a surface texture resembling that of a porous wood. The wood of the gymnosperm family of trees is non-porous and that of the angiosperms is porous. In the latter the pores may be large and concentrated in the spring wood as in oak. Such woods are referred to as ring porous. Or the pores may he randomly distributed, in which case the woods are referred to as diffuse porous woods.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there are many modifications, substitutions and alterations thereto, within the scope of the following claims.

I claim:

1. The method of working the surface of a naturally occurring wood grain panel to impart to said surface an appearance resembling that characteristic of a porous hardwood surface; said method including the steps of (1) moving said panel surface in the direction of said naturally occurring grain and along a predetermined path at a predetermined speed, (2) moving a work member surface including randomly disposed coarse grit abradant elements through a path intersecting said predetermined path at a pronounced angle to said surface, (3) passing said grit through a shallow subsurface are substantially parallel to said predetermined path at a speed differing from said predetermined speed by an amount maintaining contact between said panel and respective individual grit elements within said are for a distance of from 4;. inch to about 3 inches along said panel surface, and (4) causing said grit to leave said surface at a pronounced angle to said predetermined path whereby shallow disconnected randomly occurring crescent-shaped grooves of irregular length, width and depth are produced in said surface.

2. The method set forth in claim 1 wherein said grit is moved through said arc in the same direction as that of the motion of said work.

3. The method set forth in claim 1 wherein said grit is moved through said are in the opposite direction to that of the motion of said work.

4. The method set forth in claim 1 wherein said steps of moving said grit elements through the prescribed path are accomplished by an abradant cylinder.

5. The method set forth in claim 1 wherein said steps of moving said grit elements through the prescribed path are accomplished by a sanding belt.

6. The method set forth in claim 1 wherein said panel is plywood, said naturally occurring grain characterized by a conspicuous difference between spring wood and summer wood, and wherein said step of passing said grit through said shallow subsurface arc removes surface wood to establish grooves passing through the juncture between said spring and summer woods to produce a jagged feathered edge at said juncture.

7. The method set forth in claim 1 wherein the ratio of said grit speed to said predetermined panel speed is within the range of about ten to one to about one hundred to one.

References Cited by the Examiner UNITED STATES PATENTS EARL M. BERGERT, Primary Examiner. 

1. THE METHOD OF WORKING THE SURFACE OF A NATURALLY OCCURRING WOOD GRAIN PANEL TO IMPART TO SAID SURFACE AN APPEARANCE RESEMBLING THAT CHARACTERISTIC OF A POROUS HARDWOOD SURAFACE; SAID METHOD INCLUDING THE STEPS OF (1) MOVING SAID PANEL SURFACE IN THE DIRECTION OF SAID NATURALLY OCCURRING GRAIN AND ALONG A PREDETERMINED PATH AT A PREDETERMINED SPEED, (2) MOVING A WORK MEMBER SURFACE INCLUDING RANDOMLY DISPOSED COARSE GRIT ABRADANT ELEMENTS THROUGH A PATH INTERSECTING SAID PREDETERMINED PATH AT A PRONOUNCED ANGLE TO SAID SURFACE, (3) PASSING SAID GRIT THROUGH A SHALLOW SUBSURFACE ARE SUBSTANTIALLY PARALLEL TO SAID PREDETERMINED PATH AT A SPEED DIFFERING FROM SAID PREDETERMINED SPEED BY AN AMOUNT MAINTAINING CONTACT BETWEEN SAID PANEL AND RESPECTIVE INDIVIDUAL GRIFT ELEMENTS WITHIN SAID ARC FOR A DISTANCE OF FROM 1/8 INCH TO ABOUT 3 INCHES ALONG SAID PANEL SURFACE, AND (4) CAUSING SAID GRIT TO LEAVE SAID SURFACE AT APRONOUNCED ANGLE TO SAID PREDETERMINED PATH WHEREBY SHALLOW DISCONNECTED RANDOMLY OCCURRING CRESCENT-SHAPED GROOVES OF IRREGULAR LENGTH, WIDTH AND DEPT ARE PRODUCED IN SAID SURFACE. 